Numerous electronic devices have been introduced to track and locate mobile assets, such as for example, trucks, rail cars, and shipping containers. Hundreds of thousands of these assets have been equipped with tracking and locating devices. The most sophisticated systems permit location of an asset to within a few feet.
More recently, systems to track and locate people have been developed. These tracking and locating devices are useful in managing persons who may be incapable or unable to seek assistance, such as for example, people with Alzheimer's disease, young children, prisoners, and military personnel. Additional systems have been used to track pets and other animals.
Transmitters and transceivers utilized in locating and tracking humans have been worn as bracelets, sewn into clothing, placed in backpacks, implanted behind the ears (U.S. Pat. No. 4,706,689), implanted subdermally (U.S. Pat. No. 5,629,678), or affixed to teeth or gums (U.S. Pat. No. 6,239,705). The entirety of each of these patents are incorporated by reference.
One such system utilizes global positioning satellite technology to track and locate inanimate objects, animals, and humans. In one form, a bracelet containing a receiver is worn by a child. Utilizing the known location of three orbiting satellites and the time it takes for a signal to travel between the transducer and each of the three satellites, a three-dimensional position of the transducer is able to be calculated.
In addition to a receiver being worn as a bracelet, systems have been used employing a self-powered, self-maintained transceiver, surgically implanted under the skin, for locating, tracking and recovering persons in distress such as for example, kidnap victims, people encountering adverse circumstances while in the wilderness, victims of heart attacks, and the like.
Other systems have been used which remain passive until remotely activated. For example, one recovery system employs a transceiver hidden within a motor vehicle and a network of fixed and mobile ground transmitters and receivers to facilitate tracking and recovery of stolen vehicles. The unit is continuously operated as a receiver until it is remotely activated. Once activated, it transmits a radio beacon facilitating tracking and recovery. Ground based fixed and mobile receiver units utilizing field strength measurements and directional receivers then are able to locate the transmitter.
Another system can be affixed to the external surface of a tooth through the use of dental adhesives or bonding agents, or it may be incorporated completely within a dental restoration, endodontically prepared root canal system, a prosthetic tooth or denture.
Location and recovery systems have also been developed using timing and triangulation methods, such as that used by the Emergency Position Indicating Radio Beacons (EPIRB). Using the global positioning satellite system, once the user activates a transmitter, the associated satellite network is capable of locating a transmitting EPIRB anywhere on the face of the globe.
Receivers and transceivers worn as jewelry, sewn into clothing, or placed in the mouth are visible and easily removable, limiting their usefulness for military, intelligence and personal protection applications. Receivers and transceivers implanted under the skin require an invasive surgical procedure to implant these devices, and additional invasive surgical procedures to repair or remove the device. For this reason, sub-dermal implanted devices have a low acceptance rate among potential users, particularly children. Receivers and transceivers implanted in the mouth involve uncomfortable dental procedures to implant these devices, and additional uncomfortable dental procedures to repair or remove the device. For this reason, intra-oral implanted devices have a low acceptance rate among potential users, particularly children. Moreover, various groups have expressed concern over the potential abuse of systems that are implanted due to the inability to easily remove the devices.
In view of the above, there remains a need for an electronic tracking device that overcomes the problems discussed above.